Add the ability to drag custom price line and change its price

Is your feature request related to a problem? Please describe.

No.

Describe the solution you’d like

Able to drag custom price line. Demo (The orders can be dragged in the price scale.)

I already have a patch implementing this. Might take some efforts to rebase and write test case etc. if this feature request is approved.

Additional context

Proposal:

1. Add boolean parameter draggable to createPriceLine().
2. Able to get “the price before dragging”. I think it should be stored as a string to preserve precisions? User can parse it later if needed.
3. Change cursor when hovering over a draggable price line or dragging.

[randalhsu]

@shaunbeh Manually build lightweight-charts with the patch:

git clone https://github.com/tradingview/lightweight-charts.git
cd lightweight-charts
git checkout -b v3.8.0 tags/v3.8.0
wget https://github.com/randalhsu/OPAL/raw/main/lightweight-charts-patch/0002-Draggable-custom-price-line.patch
git am 0002-Draggable-custom-price-line.patch
npm install --legacy-peer-deps
npm run build:prod

You need to use this file: dist/lightweight-charts.standalone.production.js

[randalhsu]

@felipecsl There’s no pull request yet. Thanks for helping, hope it gets merged soon.